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Time Deposits - Additional Information (Detail) - USD ($) | Dec. 31, 2016 | Dec. 31, 2015
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Investments Schedule [Abstract] |  |
Deposits not covered by deposit insurance | $ 122,200,000 | $ 120,000,000

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- Definition Deposits not covered by deposit insurance. + References No definition available. + Details
Name: | banf_DepositsNotCoveredByDepositInsurance
Namespace Prefix: | banf_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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- References No definition available. + Details
Name: | invest_InvestmentsScheduleAbstract
Namespace Prefix: | invest_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration